According to the publications of the World Health Organism (WHO), there are nine types of brain tumors. Glioma is the most frequently found brain tumor, and cannot be easily diagnosed at its early stage, and it grows quickly. Although glioma can be removed through a surgical operation, the effect of the operation is generally unsatisfactory. Up to the present, glioma is still considered clinically as a problematic neurodisease. Glioma may result from mutation of normal glial cells in various brain regions. The growth of the tumor is accompanied with pathological symptoms such as elevated brain pressure, headache, vomiting, loss of sight and epilepsy. Most patients die within one year after the onset of glioma (Benedetti et al., 2000).
A previous study indicates that glioma cells release a large amount of glutamate, resulting in an elevated glutamate concentration in the periphery. The elevated glutamate concentration results in excitotoxicity to the surrounding neurons, and the damage to the neurons in turn promotes the growth of the glioma cells (Takano et al., 2001). Therefore, the reduction of the damage resulting from the excitotoxicity to neurons should be able to inhibit the growth of glioma cells.
Another study indicates that the elevated Ca2+ concentration within glioma cells increases cell activity and thus contributes to the migration of glioma cells. Therefore a Ca2+ channel blocker, such as MK801, can effectively inhibit the proliferation of glioma cells (Ishiuchi et al., 2002). However, MK801 is an antagonist of NMDA receptors, and will result in serious side effects when administered to patients.
Chuanxiong, a Chinese herbal medicine, is generally used in the treatment of brain vascular or cardiovascular embolism. Tetramethylpyrazine (TMP) is one of the major components in chuanxiong. Most of the TMP-related research focuses on the cardiovascular system. Relevant studies indicate that TMP can inhibit the increase of the concentration of calcium (Pang et al., 1996). As to the effect of TMP on neurons, we find TMP can reduce the excitotoxicity to neurons induced by kainite through protecting mitochondria and inhibiting the free radical generation (Shih et al, 2002).
It has also been reported that TMP can cross the blood-brain barrier (Tsai and Liang, 2001).